Field
Implementations of the present disclosure generally relate to an apparatus for processing a substrate. More particularly, implementations of the present disclosure relate to an improved electrode assembly disposed at an upper end of a processing chamber.
Description of the Related Art
In the fabrication of semiconductor devices, plasma processing chambers are commonly used to perform various fabrication processes such as etching, chemical vapor deposition (CVD), and physical vapor deposition (PVD). Generally, a vacuum pump maintains a very low pressure within the plasma processing chamber while a mixture of process gases continuously flows into the chamber and an electrical power source excites the gases into a plasma state. The constituents of the process gas mixture are chosen to effect the desired fabrication process.
In some conventional plasma processing chamber designs where plasma is generated in a cavity defined between a cathode electrode and a ground anode electrode, ion bombardment of metal electrodes may generate unwanted particles. For example, fluorine ions may bombard the cathode or ground anode electrodes made of aluminum or an aluminum alloy and generate unwanted aluminum fluoride (AlFx) particles that may contaminate a substrate being processed in the chamber. In some dry etch processes, such as one utilizing ammonia and fluorine-containing gases, the ammonia and fluorine-containing gases are introduced as a gas mixture into the cavity while a RF power is applied between the cathode electrode and the ground anode electrode to generate plasma from the gas mixture. As the cathode electrode would require higher RF power to break down both ammonia and fluorine-containing gases in the gas mixture, the substrate contamination issue caused by ion bombardment of the electrodes, especially the cathode electrode, is aggravated.
Therefore, there is a need in the art for an apparatus that effectively reduces the generation of contaminating particles on a substrate surface during plasma processing.